Heretofore, for integrated circuits which require transmission of high frequency signals in a millimeter wave band, microstrip lines, dielectric lines, and waveguide lines, and the like have been used. In particular, since a nonradiative dielectric line (NRD guide), which is one type of dielectric line and has been disclosed in Japanese Examined Patent Application Publication No. 1-51202, can suppress radiation loss of energy, superior transmission properties of high frequency signals can be obtained.
FIG. 7 shows the structure of a general NRD guide 10. The conventional and general NRD guide 10 has the structure in which two conductive plates 1 and 2 approximately parallel to each other sandwich a dielectric strip 4 having a width smaller than that of the conductive plates 1 and 2. Parts 3 between the two conductive plates 1 and 2 other than the dielectric strip 4 are voids (air). As described above, in the conventional NRD guide 10, since the width of the dielectric strip 4 is smaller than the width of the conductive plates 1 and 2, and the contact area therebetween is small, when the NRD guide 10 is handled, it is difficult to ensure the strength to retain the structure described above. Techniques for ensuring the strength of the NRD guide 10 have been disclosed in Japanese Unexamined Patent Application Publication Nos. 3-270401, 6-45807, and 8-65015.
For example, in Japanese Unexamined Patent Application Publication No. 3-270401, in order to increase the contact area between the conductive plate and the dielectric strip, a technique has been disclosed in which the dielectric strip is formed to have an H-shaped cross-section. In addition, in Japanese Unexamined Patent Application Publication No. 6-45807, a technique in which dams are provided for the conductive plates along the dielectric strip has been disclosed; and in Japanese Unexamined Patent Application Publication No. 8-65015, a technique has been disclosed in which projections are provided on a surface of the dielectric strip to be bonded to the conductive plate and are then buried therein. Accordingly, when the dielectric strip and the conductive plate are bonded to each other, the alignment can be easily performed, and the displacement of the bonding portion can be prevented.
In addition, in Japanese Unexamined Patent Application Publication No. 6-260814, a technique has been disclosed in which in order to improve the productivity of the NRD guides, top-half parts and bottom-half parts are produced separately and are then assembled into the NRD guides, and in Japanese Unexamined Patent Application Publication No. 2001-7611, a technique has been disclosed in which as a method suitably used for mass production of the NRD guides, a resist process is used.
However, according to the conventional structures and production methods of the NRD guides described above, various machining steps must be performed for the conductive plates and the dielectric strip, and as a result, there has been a problem in that those mentioned above cannot be suitably applied to mass production.
In addition, there has been a limit to ensure the strength by the bonding portions between the two conductive plates and the dielectric strip, and hence there has been a problem in that a sufficient strength cannot be obtained.
Hence, the present invention was made in consideration of the situations described above, and an object of the present invention is to provide a dielectric line and a production method therefor, the dielectric line capable of ensuring a sufficient strength and being suitable for mass production.